Altitude controller



July 24, 1956 J. H. PURL 2,756,009

ALTITUDE CONTROLLER Filed Sept. 20, 1951 SENSE VESSEL JOHN H. PURL Nam:

United States Patent ALTITUDE CONTROLLER John H. Purl, United States Navy Application September 20, 1951, Serial No. 247,541

4 Claims. (Cl. 24477) (Granted under Title 35, U. S. Code (1952), see. 266) My invention relates to improvements in altimeters, and particularly to altimeters of the altitude controller type.

The principal object of my invention is to provide means for maintaining an airplane at a constant barometric pressure altitude.

The single figure of the drawing is a schematic showing of my device including the necessary electrical connections.

In the drawing, wherein for the purpose of illustration is shown a preferred embodiment of my invention, the reference numerals and 11 designate cylindrical vessels having their open ends closed by diaphragms 12 and 13 secured thereacross, respectively. Vessel 10, called the sense vessel, has an enclosed volume of approximately 58 cubic inches; vessel 11, called the rate vessel, has an enclosed volume of approximately 19 cubic inches. The rate vessel communicates with a cooperating vessel 14, having a volume of approximately 231 cubic inches, through means of tubular element 15.

Centrally of diaphragm 12 is attached one end of a rod link 16 of insulated material, the other end of which is pivotally secured to sliding contact arm 17. Said sliding arm has one end pivotally mounted at 18 on an insulated bearing, while the other end 19 is slidably engaged with a resistance element 20 of approximately 400 ohms. Said resistance arm, link and diaphragm are constructed and arranged so that the arm normally engages the resistance at its electrical center when the diaphragm is unflexed.

Attached to arm 17, on diametrically opposite sides thereof, are two insulation lugs 21 and 22 which coact with companion lugs 23 and 24 carried by conducting arms 25 and 26 pivoted at 27 and 28 on insulated bearings, respectively. Arms 25 and 26 are normally held in a closed position against fixed contacts 29 and 30, respectively, by means of tension spring 31 of conducting material.

A 100 ohm resistor 32 has one end connected to fixed contact 29 and the other end to arm 17 through pivot 18 and through means of a variable tap 33. Said vanable tap takes off a portion of the voltage applied to the end of resistor 32 of approximately 100 ohms, and transmits it to the arm 17 for the purpose of effecting a sensitivity adjustment.

Fixed contact 30 is connected to ground 34 through a relay coil 35 of approximately 250 ohms. Relay armature 36 is provided with a cap valve portion 37 that cooperates with valve seat 38 surrounding the outlet end of tubular element 39 which communicates with the inside of vessel 10. Said cap valve is thrust open to provide communication between the sense vessel 10 and the atmosphere by compression spring 40 when relay coil 35 is de-energized.

Centrally of diaphragm 13 is attached one end of a rod link 41 of insulated material, the other end of which is pivotally secured to sliding contact arm 42. Said sliding arm has one end pivotally mounted at 43 on an insulated bearing, while the other end 44 is adapted to be 2,756,009 Patented July 24, 1956 slidably engaged with split resistors 45, each of said resistors being approximately 200 ohms. Insulated lead springs 46 and 47, anchored at 48 and 49, and bearing against slidable arm 42, are urged against abutments 50 and 51, respectively, with an initial pre-set restoring force to return the sliding arm to a centered position between said split resistors. Said split resistance, arm, link diaphragm and springs are constructed and arranged so that the arm is centered between said split resistors when the diaphragm is unfiexed.

Attached to arm 42, on diametrically opposite sides thereof, are two insulation lugs 52 and 53, which coact with companion lugs 54 and 55 carried by conducting arms 56 and 57 pivoted at 58 and 59 on insulated bearings, respectively. Arms 56 and 57 are normally held in a closed position against fixed contacts 60 and 61, respectively, by means of tension spring 62 of conducting material connected across said arms.

A resistor 63 of approximately 100 ohms has one end connected to fixed contact 61 and the other end to arm 42 through pivot 43 and through means of a variable tap 64. Said variable tap takes off a portion of the voltage applied to one end of said resistor 63 and transmits it to the arm 42 for the purpose of sensitivity adjustment.

Fixed contact 60 is connected to ground 65 through a relay coil 66 of approximately 250 ohms. Relay armature 67 is provided with a cap valve portion 68 that cooperates with valve seat 69 mounted around the outlet end of tubular element 70 that communicates with the inside of rate vessel 11. Said cap valve is thrust open to provide communication between said vessel and the atmosphere by compression spring 71 when relay coil 66 is de-energized.

A bleeder needle valve 72 is provided in communication with rate vessel 11. Said bleeder valve allows the density of the air inside the rate vessel to approach the density of the outside air at a rate determined by the setting of the needle valve and the pressure differential. The setting of the bleeder needle valve is such that the rate means does not augment the climb or dive current, hereafter described, for normal changes in altitude of the airplane. However, it does augment the current in the circuits only when the rate of change in altitude is rapid enough to overpower the bleed setting.

My altitude controller is designed to Work with a precessing type autopilot 73 having climb and dive precessing coils 74 and 75, respectively. The output of my controller is fed to said autopilot precessing coils and causes precession of the pitch attitude stabilizing gyro. By my means the pitch attitude of the airplane is caused to vary in climb or dive so as to correct for variations of altitude.

Resistor 32 is connected to the positive side of the grounded 24 volt supply potential which energizes the autopilot, through prong 76 of a standard 3-prong plug 77 by a control switch 84. Resistor 20 is connected across series connected climb and dive precessing coils 74 and 75, through prongs 78 and 79, respectively. The common connection between said coils is grounded. Contacts 80 and 81 are provided at the ends of resistor 20 and in circuit with prongs 78 and 79, respectively. The contacts are disposed to contact arm 17 when arm 17 moves to its extreme positions on resistor 20.

Resistor 63, companion to resistor 32, is likewise connected to the positive side of the supply voltage through prong 76. Split resistors 45, companions to resistor 20, are likewise connected across the climb and dive precessing coils through prongs 78 and 79, (provided at the ends of split resistors 45 and in circuit with prongs 78 and 79), respectively. The contacts 82 and 83 are disposed to contact arm 17 when arm 17 moves to its extreme positions on resistors 45.

Switch 84 controls the supply voltage to my device.

Operation When air valve 37 is closed the diaphragm 12 of the sense vessel will react to pressure differences between inside and outside air in the same manner as a barometer. That is, if the air pressure outside is more than that inside the vessel the diaphragm will respond by moving inwardly; and if the pressure outside is less. than that inside, the diaphragm will respond by moving outwardly.

When the pressures inside and outside the vessel are equal the sliding arm 17 assumes a position on the electrical center of resistor 20, thereby allowing equal amounts of current to be sent through the climb and dive precessing coils 74- and 75 resulting in a cancellation of their effects.

If the pressure outside is greater than that inside the sense vessel (this would occur if the airplane dropped in altitude) the sliding arm 17 would be actuated to the right a distance proportional to the difference in pressure between the outside and inside air (and thus to the distance dropped). More current is then sent to the climb circuit and less to the dive circuit resulting in a net balance to precess the autopilot in climb. As the plane gradually approaches its initial altitude, the inside and outside pressures tend to equalize and the sliding arm 17 tends to approach and finally returns to the center position of the resistor 20.

If the pressure outside is less than that inside the sense I vessel '10 (this would happen if the airplane suddenly Went up in altitude) the sliding arm 17 would be actuated to the left a distance proportional to the difference in pressure between the inside and outside air (and thus to the distance that it went up). More current is then sent to the dive circuit and less to theclimb circuit resulting in a net balance to process the autopilot in dive. As the plane gradually approaches its initial altitude the outside and inside pressures tend to equalize and the sliding arm 17 tends to approach and finally returns to the center position of the resistor 20.

In the event the difference in pressure is so great that the sliding arm 17 is moved to the extreme right or left it pushes against contacts 80 or 81 as the case may be and thus applies the full voltage available on the arm, as

predetermined by the sensitivity position of the tap 33 on resistor 32, to either the climb circuit or the dive circuit depending to which end of the resistor 20 that the arm 17 moves to.

Energizing potential for the air valve relay coil 35 is supplied through contact 29, through spring 31, through contact 30, to relay coil 35 and to ground. There is no electrical connection between spring 31 and sliding arm 17. At the instant that the sliding arm 17 makes contact with contact 81 it opens the relay circuit at contact through means of moving lug 22 attached to arm 17. This de-energizes the relay and the valve 37 is urged open by compression spring thus allowing air inside the sense vessel 11) to approach the same density as that outside. As the diaphragm 12 approaches its center position the sliding arm 17 approaches its center position and consequently contact 30 is closed thereby energizing relay coil 35. The energized relay coil 35 attracts armature 36 and its associated valve to a closed position thus clamping the altimeter to a new altitude. By these means the relay circuit protects the diaphragm from injurious difierential pressures and also provides means for clamping the altimeter at whatever altitude the plane happens to be. The altimeter does not function until a voltage is supplied through pin 76 when plug 77 is plugged into a provided receptacle, or when controlled by switch 84. At the instant a voltage is applied the altimeter will function and automatically be clamped by the relay at that particular altitude.

The rate vessel 11 has a bleeder needle valve 72 which allows the density inside the rate vessel to approach the density of the outside air at a rate determined by the setting of the valve and the pressure differential. The setting of the bleeder valve '72 is such that the rate vessel does not furnish any climb or dive current for normal changes in altitude of the plane. It provides additional current to the circuits only when the rate of change in the altitude is sumcient to overpower the bleed valve setting.

The rate vessel is provided with a diaphragm 13 which acts in the same Way as the diaphragm 12 in the sense vessel it). The motion of the diaphragm is transferred through link 41 to sliding arm 42 which wipes on split resistors 45.

The voltage is applied through the plug prong 76 and is conducted to one end of resistor 63. A part of this voltage is taken oii the resistor by means of variable tap 64 and is applied to the sliding arm 42 through pivot connection 43. The normal setting of the resistor 63 is such that a greater voltage is applied to the sliding arm 42 on the rate end than that supplied to the sliding arm 17 on the sense end at full deflection of the arm 42.

When the sliding arm 42 is in the center position no electrical connection is made to either of the split resistors 45, thus eliminating any current flow except when the rate vessel is called on to operate.

If the pressure outside the rate vessel .is greater than that inside the rate vessel (which would result if the airplane suddenly dropped in altitude at a rate greater than the rate at which the bleed valve 72 could equalize the pressure) the sliding arm 42 would move to the left a distance proportional to the diiference in pressure between the outside and inside air (and thus to the rate it dropped), current would be fed to the climb circuit and would add arithmetically to that supplied by the sense end. This results in a faster climb signal being applied to the climb precessing coil in the autopilot. As the rate decreases due to climb precession and the bleed equalizes the pressure the sliding arm 42 is returned to the center position. Thus this added current is removed and the current supplied to the climb circuit by the sense end is the governing factor in the climb precession of the gyro. In returning to altitude if the climbing rate exceeds the bleed setting of the rate end, then the sliding arm 42 moves to the right and supplies current to the dive precessing coil of the autopilot. This effectively lessens the climb precession rate or may even reverse the precession direction to dive if the rate is of sufiicient magnitude to give full signal.

Likewise if the pressure outside is less than that inside the rate vessel (which would result if the airplane suddenly went up in altitude at a greater rate than the bleed couldequalize the pressure) the sliding arm 42 would move to the right a distance proportional to the difference of pressure between the outside and inside air (and thus to the rate it climbed). Current would be fed to the dive circuit and'would add arithmetically to that supplied by the sense end. This in turn would result in a faster dive signal being applied to the dive precessing coil in the autopilot. As the rate decreases due to dive precession, and the bleed equalizes the pressure, the sliding arm 42 is returned to the center position. Thus this added current is removed and the current supplied to the dive circuit by the sense end is the governing factor in the dive precession of the gyro. In returning to altitude, if the diving rate exceeds the bleed setting of the rate end, then the sliding arm 42 moves to the left and supplies current to the climb precessing coil of the autopilot. This effectively lessens the dive precessing rate or may even reverse the precession direction to climb if the rate is of sufficient magnitud to give a dominating signal.

As on the sense end, if the difference in pressure between the outside air and that inside the rate vessel is so great that the sliding arm 42 is moved to the extreme right or left it pushes against contact 83 or 82, respectively, and thus applies full voltage available on the arm,

as predeermined by the position of the tap on the sensitivity resistor 63, to either the climb or the dive circuit depending on which of the split resistors 45 the arm is in contact with. The protection circuit for the diaphragm 13 is the same as that on the sense end. Normally 24 volts is applied to one end of the resistor 63 and fed through contact point 61, through spring 62 and out through contact 60 to relay 66 and to ground 65. As in the case of the sense end, there is no direct electrical connection between this branch of the circuit and the sliding arm. When the sliding arm 42 makes contact with contact 83 or 82 it opens contact 61 or 60, respectively, which are held normally closed by spring 62. This de-energizes relay 66 resulting in the valve 68 being forced open by compression spring 71. This allows the air inside the rate vessel to approach the same density as that outside. As the diaphragm approaches its center position, the sliding arm 42 approaches its center position and thus contact point 61 or 60 is closed which again energizes the relay 66. Valve 68 is thence actuated to its closed posi tion, thus restoring normal operation. Thus protection is afforded to the diaphragm 13 from too great a differential in pressure which might injure it.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What I claim is:

1. Altitude control means for aircraft, comprising; potentiometer means having a resistor with output terminals and a first slidable contact arm with input terminal means; a first fluid pressure responsive device having a safety relief vent, and constructed and arranged to actuate said first slidable contact arm; a first means for controlling said vent operative by said first slidable contact arm; a split resistance connected across said output terminals; a second fluid pressure responsive device having a vent; a second slidable arm engageable with said split resistance, actuable by said second device and having an input terminal electrically connected to the input terminal means of said potentiometer means, a second means for controlling the vent of said second device operative by said second arm; and bleeder means for said second device, having an adjustable setting.

2. Altitude control means for aircraft comprising first and second pressure responsive expansible chambers, normally closed electromagnetically operated relief valve means on each chamber, a rate valve means on said second chamber, a first slideable contact arm actuated by said first expansible chamber, a second slideable contact arm actuated by said second chamber, a first resistor having two output terminals, said first contact arm being normally biased to contact the center point of said first resistor, a split resistor having two sections, each section having an output terminal, said second contact arm being normally biased between the two sections of said split resistor, a source of voltage connected in circuit with said contact arms, and limit switch means for each of said contact arms, respectively, and actuated in response to predetermined pressure conditions by said respective contact arms for opening said electromagnetically controlled relief valve means.

3. Altitude control means for aircraft having a gyroscope and gyroscope-precessing means, the combination comprising a first means including a first pressure responsive chamber for controlling an electrical circuit having a first output variable in proportion to change in ambient pressure, said first means including variable resistance means for adjusting said first output, said first means further including first limit means for rendering said first means non-responsive and for automatically recalibrating said first means, a second means including a second pressure responsive chamber for controlling an electrical circuit having a second output which is variable in proportion to rate of change of ambient pressure, said second means including variable resistance means for adjusting said second output, second limit means for said second means for rendering said second means non-responsive, and means for combining said first and second outputs for controlling said gyroscope-precessing means in accordance with said changes.

4. Altitude control means as defined in claim 3 wherein said limit means for said first and second expansible chamber comprises a normally closed electromagnetically operated release valve on each of said chambers.

References Cited in the file of this patent UNITED STATES PATENTS 

